N62 Z3 Part 11: Fabrication (Subframe)

This is an exciting part of the build to get started. I had measured a long time ago what needed to be cut on the subframe and it's been one of those "major task" sort of things that I've been waiting to knock out


We decided to double check markings from moths ago so I got the engine back in position. We ended up using all my original markings though which was cool and got cutting

I was working with my buddy Victor to weld it and he just wanted to put plates over the now open end and call it a day. I wanted to reinforce it a little bit... I'll get into that in just a moment. My phone died so we kind of skip over a little of the process but I'm not hiding anything here - there are some ugly welds, I'm not an expert and I know that. But this is what we ended up with, with a stock subframe on the bottom for comparison

I was about to leave for the day then I thought... nah, I have to test fit it! I had left the engine in place from earlier when we were checking the fitment so it was pretty easy to do so. It went right in! It's bolted in in the below picture!

And for the area that mattered...

If anything I could have cut it a little less but it was very difficult to take measurements of it while the oil pan was interfering so I eyeballed it awhile ago and we re-eyeballed it today. All things considered I am quite happy with it - it's not even done yet though! Still needs the bottom seam welded, going to fill in those big holes, may gusset some parts of it...


So on to how I wanted to reinforce it. My fabricator's original idea was as below - just to sort of "cap off" the ends

I found a plate that was the right size for this inner width

We cleaned it up and stitched it in along the inside on that front area


Then I thought we could just extend the "sides" down to this base

I don't know, I guess my idea was it would form a box and make things a little stronger. I also was hoping adding more material to that inside front edge would strengthen it to make up for all the material we took away


Oh and since I threw the subframe in, may as well throw the steering linkage in too?

It's very close... in person is much more promising. It's also not on the threads at the firewall, just sitting roughly in place. Once its on the threads, it will move rearwards a bit, which will also move it down slightly, both of which should give it more clearance. That coupled with a smaller diameter aftermarket shaft should make this trivial (knock on wood!)

The next day I wasn't able to get to the subframe as I had other work earlier in the day, but I went in later in the night to do a little cosmetic upgrade

Started by removing the trunk ignition cylinder and harness

Then I swapped on the M trunklid. I will have to finish wiring in the electrical harness tomorrow - it is quite a pain, on the Z3 they used these huge connectors for some of the things and that makes it very difficult to fish out of the relatively narrow passageways between the sheetmetal

But, this is roughly how it looks now

That trunklid has actually been in storage with me for... 6 years now come to think of it. It's definitely picked up a little dirt, not that the car itself is much cleaner. The alignment needs to be adjusted as well - that was just my first go at it. But I just wanted to do a little something different tonight. Now back to the regularly scheduled programming...


Lower x-brace bolted into place

There is plenty of clearance between the x-brace and the oil pan and honestly, I could have cut it so that the inner bolt holes for the x-brace were kept intact. I will add a section back into the subframe to allow the inner x-brace bolt to mount, otherwise I don't think it will strengthen as effectively as it can - it needs to be triangulated on both sides to be effective at distributing forces away from the subframe


So the next day I thought my pedal assembly showed up so I could at least get that wrapped up...

That's a weird looking pedal assembly! Obviously ends up it was the bandfile, disassembled it fit into about a pedal assembly-sized box... go figure. DEI gold heat rejection tape showed up too, just so pretty to look at... this will line the transmission tunnel and maybe DME box

I never found a reference photo for how much you really get in a roll - so here you go

This is the 2" x 30' - seems like a plentiful amount, I'll have a better idea once I start using it

The next day I took an adventure to the local welding store. I spoke to a gentleman there about my project and my goals with welding for awhile and he almost, almost sold me on an $1,200 welder I absolutely did not need. He was an honest guy, just one of those... welder salesman types. Reminds me of literally every tool salesmen I've ever met. Anyways, he said I'd save money by just outsourcing the work and really recommended a local guy and gave me his card - another local enthusiast recommended a welder as well so I have two pros to talk to now which is great. I'll talk to both of them and see who feels more confident in fiddling with my frame rail. I explained to the salesman my goals for doing more work like this in the future and he agreed it'd be a good skill to learn given where I'm at. He recommended a couple textbooks and I stopped at a bookstore on the way home to pick them up


Took a little cruise with my girlfriend in the afternoon to clear my head a bit, which was much needed, I needed to re-prioritize things a bit

Got home to tons of boxes of parts sitting by my front door... haven't gone through what all of it is yet. I did open and inspect that Uro coolant pipe and I was pleasantly surprised. I'll go over it tomorrow in more detail

I then went back in to the shop later that night and spent some time stripping and cleaning the radiator core support in preparation for paint, whenever that happens

With that done, I took a look back at the pedals. I had a spare set of pedals from a Z3 3.0 I parted out which had the pedal potentiometer built in. I decided to use this instead of the floor mounted pedal in order to do it more like I thought BMW would do it


On the left is an E36 or Z3 style manual pedal assembly, on the right is a 2001-2002 Z3 pedal assembly, with the pedal potentiometer motor mounted in place (the black cylinder on the right)

The task was simple - swap the manual pedals over to the assembly for the bracket with the motor

The brake pedal shaft stays pretty clean because it's in use on the automatic car, so it's just a matter of cleaning things and swapping them over - here you can see the brass bushing fit in place. These plastic bushings in the background were in really good shape but I am really glad I went ahead and ordered these brass ones

The clutch pedal shaft was not as nice since it didn't have a pedal over it on the automatic car and has been exposed to moisture in the atmosphere, so I cleaned it up a little bit - just enough the brass bushings were a snug fit. I really didn't want to go crazy removing excess material here so it may still look a little ugly. I stopped when the bushing test fit nicely

All wrapped up

Brass bushings in place, mmm

I did lose the little white button plunger that sits in the clutch switch... I should have plenty of spares to pluck from though. I got it bolted in with the top bolt and as much as it was nice to see the pedals removed, it was even nicer seeing some pedals back in here! To finish bolting this in will require painting the engine bay first but I will also go ahead and throw the accelerator pedal back in here soon shortly too

I ended up getting a new pedal from FCP, it wasn't very expensive and I didn't like the condition of the one I removed to re-use it for the Z3 DBW setup. It arrived and was installed so now all the pedals are in place...

I also went ahead and unplugged all the modules... so now when the fabricator has time to do the chassis welding, I hopefully won't be frying modules in the process


When my bandfile belts came in I just had to play with that a bit. Engine removed so I could gain access to everything and to get ready to finalized the subframe


Then I got to work with the bandfile. Never used one of these before but it's pretty similar to a lot of abrasive tools I've used on my rotary tool... just, way better at it's job. Here's an example of one bracket, you can see part of the remnants were left behind. One thing I do know is the goal is to work the high area down, instead of working away the underlying material

Then it gets just a little primer for rust protection, but all these areas will eventually be sanded back down before final paint

Another before and after example of an area below. I am not an expert at this process


A couple other brackets were cut to be marked off, I was comparing to the Z3 I drove in with to know which I could cut and which I needed. I am not shaving the bay, just removing brackets for the 6 cylinder engine's intake as well as the washer reservoir on the opposite side. So the studs for ground cables and for cable routing I am keeping

At the end of the day the car looked about like this...

Definitely starting to look more and more like a project car...


Got ahold of the welder the welding shop recommended and he is backed up for a couple weeks but said he should be able to do it. I have another local enthusiast I will meet up with to see if he can help in the meantime, I really don't want to wait, I'd like to keep the momentum building on this project. Truthfully, I am also having second thoughts about just buying a welder...


Dug out the driveshaft again today and split it apart - the front half with the blue line is the part that will be modified/shortened, then the whole assembly will be balanced together. This is work that will be outsourced to a driveshaft shop.

The last major obstacle besides fabrication between me and a "bare bones" running car is the cooling system stuff... I've got the routing for that figured out now, just need to sort out where to fit the heater core valve and then run the hoses


Back at the next day to finish off those last brackets, had the girlfriend's brother there so I got some action shots

Then the other shock tower, with the bracket removed but before bandfiling. I really enjoy this process. Maybe next build, I will shave an engine bay...

I know I'll have to do something to clean up the seam sealer at some point...

The transmission tunnel was also finished all the way back and hit in a light dusting of primer where bare metal was exposed

While figuring out the cooling system stuff the other day I couldn't help but think that my heater core has been open, exposed to the elements for awhile... so I decided to flush it and fill with fresh coolant, just to try to keep it healthy. Those are a huge pain to replace

I then went home and researched welders some more. This was all done on a Sunday when the welding shop was closed but if they were open I probably would have bought a welder. I'm kind of glad now that the shop was closed - that extra day of research led me to buying a different welder... I had to buy it online though


After the welder showed up. If only I knew how to use it... haha. I will say, I know I'm not a welder, but I did get to feel and touch quite a few welders in person at the store and this one feels like really good quality in comparison. I'm really excited to get to set it up and start practicing with it

All loaded up. The coupe didn't skip a beat with a trunk full of welder and a passenger

And after a little practicing... not all my welds, I'll do a clean plate with just my welds later today

Yes, I welded a used transmission mount to the metal plate. It ended up being very securely attached if that's worth anything lol

The next day I did something a little more useful upgraded my press... the knob to "lock" these is usually actuated by the handle end, which is annoying - a common upgrade is to weld on a knob. I wanted it to be extended a little bit and knurled on the end. This is part of an M54 VANOS assembly and it was perfect - so now I don't need to use the handle to lock the jack on the press anymore!

I also couldn't help but notice the shape of that thing looked like the head of a little dude...

Some more practice

This stuff was pretty thick...

And back on track with the swap, really excited about this little bit... we will get to this later

At this point the engine gets it's own little build thread here while the fabrication stays focused in this section


Bought an exhaust from an E92 M3...

Looks like the pipes are pre-shaped to fit about the right shape for the Z3 chassis though I won't know that for sure until I mock it up in place. The collector pipes can be cut at a width where they line up to the N62 pipes for sure though. So it seems like it'll all work well with some rough measurements. Best part though? I paid $500 for it and sold the catalytic converters off it for $660!


Then I bought a new tool... a battery operated angle grinder. Milwaukee, of course

And I was finally able to remove the SAP bracket. It was just too much for my dremel...

And full disclosure. I did a whoopsie here... when trying to remove it, I got a little ahead of myself with the chisel. I thought the firewall was a little thicker metal than what it was and ended up poking a hole straight through it

So if you are wondering why it looks like there are welding marks in the area, it's because I had to weld the hole from the chisel hole back up. I dumped some water into the hole, to get the carpet on the other side of the firewall wet, to try to prevent it from... you know, catching fire, and welded away. Will need a little more finishing work, but I'm actually very happy with where this ended up

Then I had the welder out and set to "Z3 firewall" settings and was sick of seeing a gaping hole in the firewall so thought, hey, I should zap that back into place. I kind of wish I took a little more time to think of a battle plan on this, as filling the gap from the cut with weld took forever and will take longer to finish cleaning the welds from here, but its still better I think than the hole in the firewall lol

Tacked up. I cleaned the piece more after this picture, it was just really hard preparing it on the bench, so I tacked it then prepped it more once in place

Double checked the wiper motor mounted up before welding it in

Then welded it in place with some very ugly welds... I am truly ashamed of these but hey, I've been welding less than a month and this metal is very hard to work on. It's thin and high carbon content. I had my welder on the lowest settings and it was still burning through. I think ideally, I would use a welder with lower settings. Or a thinner wire? I'm not really 100% sure, obviously I'm still learning. I made what I had work... what's that saying? You are either a good welder or a good grinder? Well I'm not good at either yet so this is gonna take me forever to get a result I'm happy with...